Could the price of progress be a hazy blue display?

Share this story

When we reviewed the Kindle Fire HDX, we were impressed with its gorgeous display. High density displays are common now, but to find a display with bright, vivid, and accurate colors is something special—not what you'd expect in a product that costs less than $250. But we did see something unusual: a blue glow bleeding in from the edge of the display. We gave the pre-release hardware the benefit of the doubt; often, early hardware isn't quite at production levels. Now that the Fire HDX is in buyer's hands, though, it seems that the blue bleed is endemic. And after doing a little research, we've discovered that the HDX's stunning display and its blue bleed are related.

The Kindle Fire HDX's 1080p 1920x1200, 7-inch display is built by LG. For movies and most UI experiences, everything looks fantastic. Open the browser, however, and you're likely to run into the problem: a faint blue haze glows along some edges of the screen, especially when the screen is mostly white. That blue bleed was evident for users that read with the light background in the Kindle app. Since reading is an integral experience to all Kindles, this problem has caused a considerable amount of consternation.

Amazon seems to be trying to get ahead of that consternation, though; if you check the order page for the Kindle Fire HDX, you'll see a little disclaimer regarding what Amazon describes as "a blue tint around the edge of the device." The company also states that "[a]ll displays have some level of light emission around the edges, and the light on the Kindle Fire HDX 7" is blue due to the technology used to render perfect color accuracy." The first part of that statement is true, but it was the second part that really got us curious.

Two factors define the quality of a display: accuracy and gamut. Accuracy is what it sounds like; when asked to display red, the screen will display red, and not something a bit more purple or orange. Gamut is a more complicated term to define because it requires me to use the term "color space." In order to describe colors digitally, they are characterized numerically by the intensity of their red, green, and blue (RGB) components. Where there are numbers, there are graphs, and where there are graphs, there can be curves. If you take a set of defined colors within a few curves, you have a color space; the percentage of that range that a display can produce is its gamut.

Enlarge/ The sRGB color space is defined by the area within the triangle.

Color spaces define the digital language of color. They allow visual artists, designers, programmers, and readers to know what is meant by "red" or "blue." Multiple color spaces exist and overlap, though the most prevalent in the digital world is sRGB.

The sRGB color space was chosen during the CRT era. Back then, even cheap models were capable of displaying at-or-near-100 percent sRGB gamut. LCDs, though, have suffered from various complications, somewhat owing to the different types of backlights used. Ideally, the backlight should produce pure "white" light so that the panel is starting with an even source from which to filter the appropriate colors. Solutions involving CCFLs and arrays of individual red, green, and blue LEDs were generally too bulky and expensive for the TV space, let alone the mobile space.

On mobile devices, the predominant solution has involved edge-lit "white" LEDs. Here, a blue LED emits light which excites a yellow phosphor, and the combined "white" light is diffused across the display. Phosphors are molecules that, when exposed to energy, emit light; in this case the actual photons from the LED excite the phosphor molecules. This approach has been refined over the last few years, which is why mobile displays look a bit less blue today than they did in 2011. The refined process hasn't improved the gamut, however. That's because the source light is a combination of yellow and blue light, lacking both red and green elements.

A Silicon Valley advanced materials company, Nanosys, has developed a solution with an awesome name: quantum dots. The blue LED's yellow phosphor and the panel layer that diffuses the combined light are both replaced by a single thin sheet embedded with microscopic red and green phosphors. As light from the blue LED excites the red and green phosphors, the result is a truer "white" light, which yields an increase in color gamut without the expense or bulk of additional colored LEDs.

Here, is where we find the source of the blue light bleeding onto the display. Amazon was right to say that all LCDs leak a little light from their backlights. When quantum dots are used, the light that leaks out is intensely blue, since there's no yellow phosphor to soften it. That blue hue won't be noticeable against dark backgrounds, but it will be visible with white backgrounds. Since light leak isn't a new problem, there are improvements that can be implemented to mitigate their effect. These improvements add cost, though, and in a modestly priced device, we can only expect so many advances.

If you spend a lot of time looking at white screens and might find blue bleed too distracting, then you should reconsider buying a Kindle Fire HDX or plan to mitigate the problem by using the dark mode in the reader app (and on our own site). Shoppers shouldn't be turned off entirely, though; the Kindle Fire HDX remains one of the best screens for your dollar, blue bleed notwithstanding.

73 Reader Comments

Would f.lux help with this at all, not the bleeding itself, but it being irritating over long term use? I've found it to be wonderful in making displays not so blinding on other devices.

Edit: Looking at their website, there doesn't seem to be an Android version, which is weird since it's on Cydia. No idea if there's something comparable that actually works on Android or a port in progress. Its absence is kind of surprising since Android has a reputation for being more customizable, though I've never actually owned an Android device.

Edit 2: Twilight and EasyEyez (which is a terrible name) claim to be similar. Not an endorsement of either, just went looking for similar apps so I'm noting that these do exist, no idea how well either one works compared to f.lux.

On jailbroken iOS, f.lux can do graphics driver level changes to the color temperature (with little to no effect on performance), but on Android they do not currently have a similar way to accomplish this. This is why you only see yellow overlays for Android to mimic the warm color temperature.

On jailbroken iOS, f.lux can do graphics driver level changes to the color temperature (with little to no effect on performance), but on Android they do not currently have a similar way to accomplish this. This is why you only see yellow overlays for Android to mimic the warm color temperature.

There are some Android apps that can do similar things, Twilight is one of those apps that I use. This is an interesting compromise, personally it wouldn't be a deal-breaker for me, but I wonder if some others, not aware of the reasons behind it, would be concerned by this. I expect the next generation would probably resolve this, not even a totally new version, just another manufacturing revision.

This seems like a problem with a pretty simple solution. Make the display a little bit bigger, but have the extra portion covered. If light bleeding through is a concern, have it set in software that those areas are always black, or possibly don't have actual pixels there at all, since it is apparently less noticeable under such conditions. I understand this would increase costs, but it seems like it would be fairly minor and produce a very large difference.

How about a software fix by tinting pixels at the edges of the screen yellow, so it cancels out? Or is there some reason why this won't fix the issue completely that I am not aware of?

Because the software would have to continuously check the value of the actual pixels to determine how much alteration is necessary (since you don't want to tint them when they're blue for example). That can be a dramatic performance impact. In addition, the screens will have variances that the software cannot account for. Finally, doing so will reduce the overall gamut possible along the edges of the screen which could be more noticeable than the glow.

How about a software fix by tinting pixels at the edges of the screen yellow, so it cancels out? Or is there some reason why this won't fix the issue completely that I am not aware of?

Because the software would have to continuously check the value of the actual pixels to determine how much alteration is necessary (since you don't want to tint them when they're blue for example). That can be a dramatic performance impact. In addition, the screens will have variances that the software cannot account for. Finally, doing so will reduce the overall gamut possible along the edges of the screen which could be more noticeable than the glow.

But in many applications (e.g. the Books app, where the tint is most obvious) there is no need to constantly re-check. The edges are either white, yellow, or black. So, just pre-calibrate those pixels depending upon which background the user has selected.

Because the software would have to continuously check the value of the actual pixels to determine how much alteration is necessary (since you don't want to tint them when they're blue for example). That can be a dramatic performance impact.

Not necessarily. Assuming that there's a OS level GL compositor doing the final render to the screen it could apply a fragment shader to the results and blend the output do modifications at GPU speeds by applying a correction based on the incoming texture pixel and the distances from the edges of the screen. That kind of modification would be nearly free in terms of runtime on a PC GPU, though I don't know what kind of impact it would have on a tablet processor or the battery life.

Would f.lux help with this at all, not the bleeding itself, but it being irritating over long term use? I've found it to be wonderful in making displays not so blinding on other devices.

Edit: Looking at their website, there doesn't seem to be an Android version, which is weird since it's on Cydia. No idea if there's something comparable that actually works on Android or a port in progress. Its absence is kind of surprising since Android has a reputation for being more customizable, though I've never actually owned an Android device.

Edit 2: Twilight and EasyEyez (which is a terrible name) claim to be similar. Not an endorsement of either, just went looking for similar apps so I'm noting that these do exist, no idea how well either one works compared to f.lux.

I tried using that once. I immediately realized it's intended for people who go to bed loooooooooooooong before I do. It's, um a bit too much for me before midnight.

Interesting tech. On the gripping hand, it doesn't matter what tech you use to get the job done. Customers will judge you by the end result and what it costs. Many a company has come a cropper from forgetting this principle.

Ah, that makes sense. A few years ago, I bought a 3rd gen retina iPad with lousy blue bleed on one side. Looking around the interwebs, this was a common problem for the early builds. I couldn't deal with it though and exchanged it for a new one that didn't have the bleed. What amazed me was that the store reps couldn't see it even against white backgrounds (maybe I shouldn't actually be amazed).

Anyway, your advice seems right on. For a Kindle Fire HDX, which is so inexpensive and otherwise terrific display-wise, the blue bleed could be tolerable. For an expensive iPad though, no way.

What about implementing in software a thin black border of pixels whenever there's white content around the edges?

From what I can see in the picture used it wouldn't be "thin" but rather significant for that device.

Possibly only to cover the entire area of the bleed. Since it's not a linear effect, covering some percentage of the area might obscure enough that the rest is barely noticeable.

Let's say the bleed is readily noticeable over 3mm (I have no idea if it is, not owning a device, but for arguments' sake). If it's ~100% at 1mm, 40% at 2mm and 10% at 3mm then covering 1mm might be enough to take it from "Wow, the border is freakin' blue" to "If I look at it carefully, I see a blue edge glow".

And...Amazon may have already done that, and the blue glow is worse outside the screen area.

Maybe it's most noticeable when you have the screen bright in a fairly dim environment? I'd be curious to mess with it a bit, if I knew someone with an HDX.

Not really. They're essentially the same concept as LED: UV/blue light strikes a phosphor that glows yellow. In LED the source is a semiconductor diode. In CCFL its a gas tube. Either way though it just comes down to the quality of the phosphor chosen. Thats why these quantum dot systems have such wide gamut and can be calibrated to be so accurate, the QD is quite high quality. But you could use the same basic technology with CCFL too if you wanted. Generally though LED is prefered because its more compact and much more power efficient.

I always get down votes when I mention Apple Cinema monitors are not very accurate due to LED back lighting.

Nonsense. If they're inaccurate at all, its because they're not well calibrated. Accuracy though is just how precisely each color corresponds to a wavelength range that your eye will perceive as a given color. Thats basically just calibration of the whole device. Even a poor quality backlight can give you highly accurate colors if properly calibrated, it will however tend to have poor gamut.

CCFT still is the way to go if you want accurate color. Of course, not very practical for phones or even notebooks. Fragile, short lived, and battery hogs, not to mention the CCFT drivers often croak.

I always get down votes when I mention Apple Cinema monitors are not very accurate due to LED back lighting.

At the moment, OLED is probably less accurate than LCD plus LED back light, but the technology is improving.

"Proper" RGB LED backlighting is at least as good, if not better than CCFL - you don't have to worry about phosphors fading unevenly over time, and you can (at least in principal) adjust backlight intensity in areas smaller than "everything". Reasonably priced white LEDs like what's being used in the HDX have lots of benefits, but amazing colour gamut isn't one of them.

Quote:

BTW, you generally check for light bleed with the LCD set to black, so I don't get why this is a problem with white.

I'm guessing dynamic backlight control means that if you display a black screen, the backlight is turned low enough to make it hard to see any blue. You have to ramp the backlight up by displaying something white(ish) to see it - though I bet you could make a test specifically for this, bright white in the center with a black border perhaps.

Not really. They're essentially the same concept as LED: UV/blue light strikes a phosphor that glows yellow. In LED the source is a semiconductor diode. In CCFL its a gas tube. Either way though it just comes down to the quality of the phosphor chosen. Thats why these quantum dot systems have such wide gamut and can be calibrated to be so accurate, the QD is quite high quality. But you could use the same basic technology with CCFL too if you wanted. Generally though LED is prefered because its more compact and much more power efficient.

I always get down votes when I mention Apple Cinema monitors are not very accurate due to LED back lighting.

Nonsense. If they're inaccurate at all, its because they're not well calibrated. Accuracy though is just how precisely each color corresponds to a wavelength range that your eye will perceive as a given color. Thats basically just calibration of the whole device. Even a poor quality backlight can give you highly accurate colors if properly calibrated, it will however tend to have poor gamut.

Not really. I use a NEC pro monitor with CCFT. Trust me, it cals just nicely with the spider.

Not to say you are posting nonsense, but well seriously, you get accurate color with a poor back light? Can we cut taxes, increase spending, and balance the budget at the same time? Just wondering...

While I'm at it, the NEC and other pro monitors have electronic field flattening.

Seriously, it is OK to use a Mac if you can't handle other operating systems, but avoid the Apple displays.

CCFT still is the way to go if you want accurate color. Of course, not very practical for phones or even notebooks. Fragile, short lived, and battery hogs, not to mention the CCFT drivers often croak.

I always get down votes when I mention Apple Cinema monitors are not very accurate due to LED back lighting.

At the moment, OLED is probably less accurate than LCD plus LED back light, but the technology is improving.

"Proper" RGB LED backlighting is at least as good, if not better than CCFL - you don't have to worry about phosphors fading unevenly over time, and you can (at least in principal) adjust backlight intensity in areas smaller than "everything". Reasonably priced white LEDs like what's being used in the HDX have lots of benefits, but amazing colour gamut isn't one of them.

Quote:

BTW, you generally check for light bleed with the LCD set to black, so I don't get why this is a problem with white.

I'm guessing dynamic backlight control means that if you display a black screen, the backlight is turned low enough to make it hard to see any blue. You have to ramp the backlight up by displaying something white(ish) to see it - though I bet you could make a test specifically for this, bright white in the center with a black border perhaps.

Trawl the net a bit. You can find display that epic fails with dynamic backlighting. There is a movie scene where the actor is in a pitch black room and turns on a flashlight. (Torch for you Brits.) You can see the halo due to the dynamic backlight scheme.

I would bet that a software update is already in the works to cover up or at least darken those pixels in all apps, with a hook for third-party apps to disable it when they want, but it wasn't ready on release. Probably a big mistake on their part to assume no one would care.

This seems like a problem with a pretty simple solution. Make the display a little bit bigger, but have the extra portion covered. If light bleeding through is a concern, have it set in software that those areas are always black, or possibly don't have actual pixels there at all, since it is apparently less noticeable under such conditions. I understand this would increase costs, but it seems like it would be fairly minor and produce a very large difference.

Better solution: calibrate the edge of the display's per channel / per pixel gain in RGB color space to tone down the blue gradient. The gain curve may even need to be somewhat non-linear as opposed to fixed based on display brightness and intended pixel color. To make it cost effective, calibrate all displays to the same average per production batch and possibly offer an app to let users further tweak the settings.

We've been able to mitigate a lot of these kinds of issues for >30 years with calibration controls in the TV market. Doesn't make much sense that the obsession with making Android and iOS devices dumb easy for the user that we take away so many settings, adjustments and tweaks that people might want.

From what I've heard/read white text on a blue background is best for readability/legability

It doesn't help with problem of looking at a computer screen all day but it does reduce to strain to trying to read all day

IIRC it's down to the receptors in your eye. Blue and yellow for example are perceived by receptors in the same area of the eye. The Amiga used a 4 color palette taken from a NASA study: black, orange, blue and yellow.

They say that green is the best for reduced eyestrain as we're best adapted to see things hiding in a green environment coming to eat us.